The Portuguese detective who led the investigation in to the unsolved disappearance of Maddie McCann has made bizarre claims about a cover-up involving the former British Prime Minister and MI5.

Goncalo Amaral, a former police officer who was removed from the case for criticising British police, told Sunday Night that he thinks the little girl was accidentally killed by her parents. He then said MI5 "for sure had an involvement" by either hiding the body or covering up the alleged murder on the orders of the then Prime Minister Brown.

Maddie's parents, Kate and Gerry McCann dismissed Amaral's theory, simply saying: "The less said about Goncalo Amaral the better".

Portuguese police have been criticised for the way they investigated the disappearance of the three-year-old, who vanished from a holiday apartment in the Portuguese town of Praia da Luz in May 2007.

Detectives then sensationally named the McCanns, who are both doctors, as "arguidos" which roughly translates to people being questioned under caution.

They were cleared by Portuguese investigators in 2010, but Amaral has continued to point the finger at the McCanns — even writing a 'tell-all' book, The Truth of the Lie which claimed they faked their daughter's abduction.

Mr and Mrs McCann were eating dinner with friends at a tapas bar nearby while their three children slept.

GP Kate raised the alarm when she returned to check on Maddie, and her twin brother and sister, around 10pm and discovered the bedroom window was open and Maddie was gone.

"I knew instantly she had been taken", she said.

Various experts who have been involved in reporting or investigating the case also weighed in with their opinions on what may have happened to the little girl from Leicestershire, UK.

Journalist Paul Luckman said she could be buried in one of the many wells in Praia da Luz, while a professor said she may have been knocked down by a drunk driver after leaving the apartment to find her parents.

Next week marks ten years since Maddie disappeared. She would have turned 14 this year.